Obatoclax (GX15-070) is Bcl-2 homology domain-3 (BH3) mimetic, antagonize all antiapoptotic Bcl-2 family proteins (average IC50, 3 umol/L), including Mcl-1 (IC50, 2.9 umol/L) and Bfl-1 (IC50, 5 umol/L).

in vitro: Obatoclax is a BH3 mimetic which binds to a broad spectrum of Bcl-2 family members, including Bcl-2, Bcl-xL, and Mcl-1. Obatoclax uniquely displaces BH3 domains by activation of the pocket of Mcl-1 followed by a triggering of apoptosis mediated by oligomerization of Bak and release of cytochrome c. Obatoclax is sensitive to Bcl-xL in cell lines lacking it or showing low expression. It shows low cytotoxicity to Mcl-1, Bcl-2, and Bcl-xL in all the strongly-expressed cell lines. Obatoclax inhibits multiple myeloma (MM) cell lines (KMS12PE, KMS18, MY5, etc.) with IC50 values ranging from 52 to 1100 nM and the inhibition is umimpaired even in the presence of IL-6 or IGF-1, which are resistance to cytotoxic agents, at a concentration of 150 nM. Obatoclax enhances the antimyeloma activity induced by melphalan, dexamethasone, or bortezomib. Obatoclax potentiates TRAIL (tumor necrosis factor-related apoptosis-inducing ligand)-mediated apoptosis by unsequestering Bak and Bim from Bcl-2/Bcl-xL or Mcl-1 proteins in PANC-1 and BxPC-3 cells.
in vivo: Obatoclax also exhibits high antitumor activity in SCID mice bearing human C33A cerivical carcinoma tumors at a dose of 0.5 mg/kg.

1. Marina Konopleva et al Mechanisms of Antileukemic Activity of the Novel Bcl-2 Homology Domain-3 Mimetic GX15-070 (Obatoclax) Cancer Res May 1, 2008 68; 

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2. Oki Y, Copeland A, Hagemeister F, Fayad LE, Fanale M, Romaguera J, Younes A.Experience with obatoclax mesylate (GX15-070), a small molecule pan-Bcl-2 family antagonist in patients with relapsed or refractory classical Hodgkin lymphoma.Blood. 2012 Mar 1;119(9):2171-2.